This invention relates to material handling systems; and more particularly relates to a novel and improved method and apparatus for stacking, unstacking and transferring pallets and pallet-like articles which are nestable together and require separation and individual transfer from a stack to another location.
Pallets are in widespread use in handling and conveying materials and customarily involve arranging the pallets in a stack, individually removing each pallet from the stack and transferring to another location where the pallet is loaded with one or more articles. Subsequently, in a depalletizing operation, the pallets are unloaded and restacked to repeat the foregoing operation and sequence. In the past, relatively sophisticated apparatus has been required to separate each pallet from the stack and advance laterally away from the stack to deposit or place on a conveyor. For example, reference is made to U.S. Pat. Nos. 3,780,884 to R. K. Jones, 4,702,660 to G. Niehaus et al and 4,960,362, to L. S. Karpisek.
Traditionally, the standard pallets in use have been flat wooden trays or platforms and which could be easily separated from a stack but were not nestable together. Accordingly, the standard pallets described are gradually being replaced by molded, preformed plastic or pressed wood pallets generally in the form of an egg carton which can be nested together and can withstand increased loading. However, a problem confronting users of the preformed pallet is to effect positive separation of each individual pallet from the stack, since the nestable pallets tend to become wedged together particularly when subjected to the weight of an entire stack.
It is proposed to simplify and accelerate the pallet dispensing operation and in such a way as to permit utilization of a portable lift in direct association with a conveyor extending beneath a stack of pallets thereby minimizing the distance and direction of movement of each pallet away from the stack and eliminating parts and components formerly required in the dispensing operation. It is further proposed to effect positive separation of nestable pallets from one another as a part of a closely coordinated sequence of steps in removing each pallet from the stack and transferring to another location.
Other representative patents in the field are U.S. Pat. Nos. 4,757,971 to W. G. Frish, 3,865,258 to G. Muller, 4,607,476 to C. B. Fulton, Jr., 4,865,515 to W. C. Dorner et al, 4,971,514 to D. F. Hunter, 4,096,367 to E. P. Sinski and 5,120,178 to M. Ito.